There have been various liquid ejectors proposed each of which ejects droplets from a head by pressurizing a liquid flow channel for use in printers, facsimiles, copiers, or complex machines thereof, various types of image forming apparatuses such as plotters or other various types of patterning devices.
In such a liquid ejector, water-repellency is generally imparted to the ejection side surface of a nozzle, because when the periphery of the nozzle surface gets wet with ejected liquid, the droplet flying direction may deviate from the normal direction, causing defective wiping of the nozzle surface.
Further, a flow channel surface for an ejection liquid in a nozzle hole, i.e., an inner wall of a nozzle hole is preferably hydrophilic from the perspective of the filling property of an ejection liquid and the meniscus stability (see Patent Literature 1, Patent Literature 2, Patent Literature 3, and Patent Literature 4). Such a hydrophilic inner wall of a nozzle hole has less up-and-down move of the meniscus and can keep the meniscus positioning constant, but the meniscus holding force is weak and the meniscus itself becomes easily broken due to a variation in pressure applied inside and outside the nozzle. Therefore, water repellency is imparted to only the region near the ejection port in the nozzle hole, similarly to the nozzle surface (see Patent Literature 5, Patent Literature 6, Patent Literature 7, Patent Literature 8, and Patent Literature 9). However, the above-mentioned proposals cause a boundary between a hydrophilic region and a water-repellent region in a nozzle hole, and thus there is a need to precisely control the position of a water-repellent layer inside a nozzle hole for all the nozzles to be used. As mentioned above, various methods have been disclosed in the prior art, however, they are not necessarily satisfactory.
Furthermore, there have been proposals for imparting water repellency to the entire inner surface of a nozzle hole (see Patent Literature 10, Patent Literature 11, Patent Literature 12, and Patent Literature 13). However, these proposals are insufficient in terms of the filling property of ejection liquid and the meniscus stability.
As described above, it is still extremely difficult to satisfy all of the filling property, ejection stability and reliability by controlling the wettability to an ejection liquid inside a nozzle hole.
In the meanwhile, liquid ejectors have become increasingly utilized for printers, facsimiles, copiers, or complex machines thereof, various types of image forming apparatuses such as plotters or other various types of patterning devices, and have become required to be used for an ejection liquid having various physical properties such as surface tension and viscosity. For example, recent inkjet printers are required to have still higher quality of images and higher durability, and actually, there have been provided various improvements in physical properties of inks as ejection liquids, for example, (1) the surface tension of an ink is reduced to increase the permeability to paper as a recording medium, thereby improving color-developing property of the ink; (2) the photo resistance and water resistance property are improved by using a pigment as a colorant for ink; and (3) the image fixing property is improved by adding a resin to an ink. Currently, it is strongly desired to provide a nozzle plate for inkjet head with which such an ink can be stably used.    [Patent Literature 1] Japanese Patent Application Laid-Open (JP-A) No. 6-40040    [Patent Literature 2] Japanese Patent Application Laid-Open (JP-A) No. 7-329303    [Patent Literature 3] Japanese Patent Application Laid-Open (JP-A) No. 2004-25657    [Patent Literature 4] Japanese Patent Application Laid-Open (JP-A) No. 2004-1494    [Patent Literature 5] Japanese Patent Application Laid-Open (JP-A) No. 63-122560    [Patent Literature 6] Japanese Patent Application Laid-Open (JP-A) No. 10-217483    [Patent Literature 7] Japanese Patent Application Laid-Open (JP-A) No. 2001-187453    [Patent Literature 8] Japanese Patent Application Laid-Open (JP-A) No. 2003-19803    [Patent Literature 9] International Publication No. WO99/15337    [Patent Literature 10] Japanese Utility Model Application Laid-Open (JP-U) No. 57-153540    [Patent Literature 11] Japanese Patent Application Laid-Open (JP-A) No. 5-345419    [Patent Literature 12] Japanese Patent Application Laid-Open (JP-A) No. 9-216370    [Patent Literature 13] Japanese Patent Application Laid-Open (JP-A) No. 2001-187447